number system sya

1. Computer Science
Class XI ( As per CBSE Board)
Chapter 4
Number System
&
Encoding Schemes
New
syllabus
2020-21
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2. Number System
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In general term computer represent information in different types of
data forms i.e. number , character ,picture ,audio , video etc.
Computers are made of a series of switches/ gates. Each switch has
two states: ON(1) or OFF(0).That's why computer works on the basis
of binary number system(0/1).But for different purpose different
number systems are used in computer world to represent
information. E.g. Octal, Decimal, Hexadecimal.

3. Decimal Number System
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Characteristics
Positional
(Most) people use the decimal number system Why?
THIS A POSITIONAL NUMBER SYSTEM .and that's of great advantage
..simple shifting the position of decimal.It become complex either
case to use number system <10 or >10.

4. Binary Number System
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Characteristics
Positional
Most (digital) computers use the binary number system Why?
Computers are made of a series of switches/ gates. Each switch has two states:
ON(1) or OFF(0).That's why computer works on the basis of binary number
system(0/1).

5. Decimal-Binary Equivalence
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6. Binary – Decimal Conversion
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Using positional notation

7. Decimal-Binary Conversion
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Using the Division Method:
Divide decimal number by 2 until you reach zero, and then collect
the remainders in reverse.

8. Hexadecimal Number System
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Characteristics
Positional
Computer programmers often use the hexadecimal number
system,Why?
Computers only work on the binary number system. The
hexadecimal number system is commonly used to describe
locations in computer memory. They are also used in
assembly language instructions.

9. Decimal-Hexadecimal Equivalence
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10. Hexadecimal to decimal
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Decimal to hexadecimal
Read from bottom
to top: 2516

11. Binary - hexadecimal
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12. Binary to hexadecimal
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Convert 1101001102 to hex
Starting at the right end, split into groups of 4:
(pad empty digits with 0)

13. Hexadecimal to Binary
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Convert 3D916 to binary
Convert each hex digit to 4 bits:
(can remove
leading zeros)

14. Octal Number System
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Characteristics
Positional
•
Computer programmers often use the octal number
system,Why?
Octal and hex use the human advantage that they can work with
lots of symbols while it is still easily convertible back and forth
between binary.

15. Decimal-Octal Equivalence
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16. Octal to decimal
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positional powers of 8:
decimal positional value:
Octal number:

17. Decimal to octal
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Using the Division Method:
Example 1:

18. Binary-Octal Conversion
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E.g.
Octal to binary

19. Binary addition
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Start at right column
Proceed leftward Carry
1 when necessary

20. Encoding Schemes/
String representation
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String is any finite sequence of characters.Any string
includes etters, numerals, symbols and punctuation marks.
Computers are designed to work internally with numbers.
In order to handle characters, we need to choose a number
for each character. There are many ways to do this ,which
are knows as encoding schemes.

21. Encoding schemes
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Following are some Encoding schemes
• ASCII
• UNICODE
• ISCII

22. Encoding Scheme
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ASCII
It is most common coding system (Pronounced ass-key).
ASCII = American National Standard Code for Information
Interchange
It is Defined in ANSI document X3.4-1977. It is a 7-bit code.Its 8th
bit is unused (or used for a parity bit)
Two general types of codes:
95 are “Graphic” codes (displayable on a console)
33 are “Control” codes (control features of the console or
communications channel)

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ASCII
Encoding Scheme

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ASCII CHART
LEAST SIGNIFICANT BIT
Encoding Scheme

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ASCII
LEAST SIGNIFICANT BIT
“Hello, world” Example
Encoding Scheme

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UNICODE
It is a worldwide character-encoding standard .Its
main objective is to enable a single, unique
character set that is capable of supporting all
characters from all scripts, as well as symbols,
that are commonly utilized for computer
processing throughout the world.
Encoding Scheme

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ISCII
ISCII stands for Indian Script Code for Information
Interchange for Indian languages. It is an 8-bits code to
represent Indian scripts.
The Department of Electronics (DOE) has established
standard and standard are in action from 1983.
These codes are used for 10 Indian scripts- Devanagri,
Punjabi, Gujrati, Udia, Bengali, Asami, Telgu, Kannad,
Malayalam and Tamil. C-DAC (established in August-
September, 1988) developed standard for font coding in
1990 is called ISFOC (Indian Standards for Font Coding).
LEAST SIGNIFICANT BIT
Encoding Scheme